This invention relates to an integrated circuit (IC) chip, and more particularly to an IC chip to be mounted on a glass substrate of a device such as a liquid crystal display (LCD), electroluminescent (EL) display, etc.
In recent years, IC chips are incorporated in not only an information processing device such as a computer, but also various machines such as a television, a household electric appliance, a motor car, etc.
FIG. 6 is a perspective view showing a liquid crystal display (LCD) 100. The LCD 100 forms an display area of the liquid crystal sealed between a first body substrate 2 and a second body substrate 3 which are made of glass. On the first body substrate 2 in the display area, switching elements 5, which are formed of a plurality of pixel electrodes 4 and thin film transistors (TFT), are arranged in a matrix. A common electrode 6 is provided below the second body substrate of the entire surface of the display area. The LCD 100 is a display device in which a voltage is applied between the pixel electrodes 4 and the common electrode 6 to drive the liquid crystal for display. On the periphery of the display area, a plurality of gate line driving ICs 101 and a plurality of signal line driving ICs 8 are arranged. A plurality of gate lines 9 are extended from the gate line driving ICs 101. The gate line driving ICs 101 sequentially select the gate lines 9 to apply gate signals so that the TFTs 5 connected to the gate lines 9 are turned on. A plurality of signal lines 10 are extended from the signal line driving ICs 8. The signal line driving ICs 8 supply a video signal to the pixel electrodes 4 through the TFTs 5 which have been turned on. The gate line driving ICs 101 and signal line driving ICs 8 are IC chips mounted on the body substrate.
Generally, the IC chip is constructed of a plurality of circuit elements each including a semiconductor film, a conductive film, an insulating film, etc. stacked on an IC substrate of semiconductor. In this specification, the substrate constituting the LCD 100 is referred to as a body substrate, whereas the substrate constituting the IC chip is referred to as an IC substrate.
FIG. 7 is a sectional view of a MOS transistor which is an example of the circuit element constituting the IC chip. The MOS transistor is structured as follows. A gate insulating film 122 and element isolation regions 123, which are formed by thermally oxidizing a silicon (Si) substrate 121, are provided on the Si substrate 121. On the gate insulating film 122, a gate electrode 124 is provided. By implanting ions into the Si substrate 121 using the gate electrode 124 as a mask, diffused layers 125a and 125b are formed in the Si substrate 121. A first interlayer insulating film 126 is provided to cover the gate electrode 124. A first wiring 127 is provided through a contact hole made in the interlayer insulating film 126. A second interlayer insulating film 128 is provided on the first wiring 127. A second wiring 129 is arranged through the contact hole made in the interlayer insulating films 126 and 128.
The IC chips 8 and 101 are manufactured as shown in FIG. 8 in such a manner that a plurality of IC chips are simultaneously formed in a semiconductor wafer 130 cut out from a single crystalline lump called “ingot” and each IC chip is separated from one another along scribing lines 131 indicated by dotted lines.
In order to make the ingot, a dedicated pot is required. The size of the semiconductor wafer cut out from the ingot has a certain limit. Therefore, the number of IC chips cut out from a sheet of semiconductor wafer 130 also has a limit. In addition, the semiconductor wafer having a large size is generally expensive. This is an obstacle to reduce the production cost.
Therefore, this invention intends to provide an IC chip capable of reducing the production cost.
Meanwhile, the IC chips 8 and 101 to be mounted on the LCD 100 are mounted on the body substrate 2 by pressure welding. In this case, the glass substrate and the semiconductor substrate have different coefficients of thermal expansion. Therefore, according to an environment to be adopted, a problem that the chip comes off may be presented. This leads to failure of the display device.